Optical Imaging Writer System

ABSTRACT

System and method for applying mask data patterns to substrate in a lithography manufacturing process are disclosed. In one embodiment, the method includes providing a parallel imaging writer system having a plurality of spatial light modulator (SLM) imaging units arranged in one or more parallel arrays, receiving a mask data pattern to be written to a substrate, processing the mask data pattern to form a plurality of partitioned mask data patterns corresponding to different areas of the substrate, identifying objects in an area of the substrate to be imaged by corresponding SLMs, selecting evaluation points along edges of the objects, configuring the parallel imaging writer system to image the objects using the evaluations points, and performing multiple exposures to image the objects in the area of the substrate by controlling the plurality of SLMs to write the plurality of partitioned mask data patterns in parallel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claims priority under35 U.S.C. §120 to United States non-provisional application bearing Ser.No. 12/897,726, filed Oct. 4, 2010, which claims benefit ofnon-provisional application bearing Ser. No. 12/475,114, filed May 29,2009, which claim benefit of non-provisional patent application bearingSer. No. 12/337,504, filed Dec. 17, 2008, which claims the benefit ofU.S. provisional application No. 61/099,495, “An Optical Imaging WriterSystem,” filed Sep. 23, 2008. This application also claims benefit ofU.S. provisional application bearing Ser. No. 61/286,342, “An OpticalImaging Writer System,” filed Dec. 14, 2009. The aforementioned UnitedStates applications are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

The present invention relates to the field of lithography formanufacturing. In particular, the present invention relates to systemand method for applying mask data patterns to substrate in a lithographymanufacturing process.

BACKGROUND OF THE INVENTION

Fast-paced technology progress in semiconductor integrated circuit (IC)industry has benefited well for the manufacturing of active matrixliquid crystal display (AMLCD) TV and computer monitor displays. In therecent years, the size of LCD TV and computer monitor displays has grownto be larger and yet more affordable.

In the semiconductor IC industry, a technology generation is defined bythe critical dimension (CD) of the circuit design rules. As eachtechnology generation progresses, the IC of the later generation hassmaller feature CD target and tighter tolerance. For the Flat PanelDisplay (FPD) industry, on the other hand, a technology generation isclassified by the physical dimension of substrate used in manufacturing.In one example, the substrate sizes (in millimeter×millimeter) of FPDssixth generation (G6) in 2005, eighth generation (G8) in 2007, and tenthgeneration (G10) in 2009 are 1500×1800, 2160×2460, and 2880×3080respectively.

The lithography challenges in terms of making semiconductor ICs and FPDsubstrates are both trying to make larger sizes more affordable.However, they are entirely different from the manufacturing perspective.For the IC industry, a primary challenge is small CD features can beproduced on a round 300 mm wafer. The goal is to pack as manytransistors as possible for achieving better functionalities in the samedie size. But for the FPD industry, one primary challenge is how largean entire rectangle substrate can be processed. The larger FPD substratecan be processed in a manufacturing line, the bigger size TVs ormonitors can be produced with lower cost. The typical LCD TVs andmonitors are designed with more sophisticated thin film transistor (TFT)for better performance. Still, the TFT CD target remains in the samespecification range. In one viewpoint, one of the main challenges forFPD manufacturing is to keep throughput in pace with justifiableeconomics for each successive generation. Achieving profitable processyield is a key consideration, and the manufacturing process window needsto be preserved.

Conventionally, lithography technologies for manufacturing of FPD arederived from lithography process technologies for making semiconductorICs. Majority of lithography exposure tools used for making FPDsubstrates are projection stepper and/or scanner systems. These areeither 2-times reduction or 1-to-1 projection from mask to substrate. Inorder to project mask patterns to the substrate, the mask must first bemade with the acceptable CD specifications. The FPD mask manufacturingprocess is similar to the one used for manufacturing semiconductor ICs,with the exception that the mask size for making semiconductor ICs isabout 150 mm or 6 inches per side, whereas the mask size formanufacturing FPD, in one example, may be nearly 8-times larger perside, or physically more than one meter per side.

FIG. 1 illustrates a conventional configuration of projection exposuretool used for scanning mask patterns onto FPD substrate. In thisconfiguration, the exposure sources used are mainly high pressuremercury (Hg) short-arc lamps. The incoming illumination light isreflected by a light folding mirror 102, and the reflected light passesthrough a mask 104, a projection lens 106 before it reaches a FPDsubstrate 108. The concern of using this conventional mask-basedexposure tool configuration as shown in FIG. 1 for the upcoming FPDlithography manufacturing is the issue of handling the increasingphysical size of masks. In one example, for the G8 FPD, the size of amask is about 1080 mm×1230 mm. The area size of G8 substrate is fourtimes larger. The TFT CD feature specification is in the range of 3microns±10%. The CD control for TFT over more-than-two-meters per sideof G8 substrate is more challenging than controlling specifications forprinting advanced IC features on a 300 mm silicon wafer. The challengefacing the FPD industry is to build such a mask-based exposure tool costeffectively for the upcoming FPD generations while preserving acceptablelithography process window.

To mitigate CD uniformity issue over the entire FPD exposure field, oneapproach is to use multiple exposures method. The nominal exposure iscomposed of several component exposures in adequate proportions. Eachcomponent exposure uses pre-selected wavelength for illumination alongwith the corresponding projection lens for scanning and stepping. Morethan one projection lenses need to be included in this type of exposuretool but only single illumination source is equipped. This is due to theneed of using high powered Hg short-arc illumination sources in kiloWatts (KW) for throughput. The selection of exposure wavelength can bedone by applying adequate filter to the source. In one example, thismulti-wavelength exposure method relaxes the negative impact on CDuniformity over a G8 substrate hence allowing more economical quality oflens and illumination set-up to be used.

In using multi-wavelength exposures, it is necessary to specify morestringent CD target and uniformity on the mask itself. In one example,the TFT mask CD tolerance is under 100 nm, much smaller than otherwisenecessary for the nominal 3 microns mask CD target. One reason is thatthe process window for FPD lithography manufacturing can be moremanageable for the existing exposure tool configuration. Unfortunately,the tighter FPD mask CD specifications required would push the alreadycostly mask set to be even more expensive. In some situations, making acritical level mask for the G8 FPD becomes very expensive and has longdelivery lead time.

Yet another problem with the conventional approach is the defect densitycontrol for the use of larger sized masks. Lithography processing withsuch a large size mask using multiple exposures, even starting withdefect free mask, is prone to introduce detrimental defects. A defectprone process impacts yield and ultimately the cost of the mask.

FIG. 2 illustrates a conventional mask making exposure toolconfiguration. In this exposure tool configuration, illumination light202 is sent to a beam splitter 204 and then partially reflected toilluminate the spatial light modulator (SLM) 206 through a Fourier lens208. Then, the imaging light rays reflected back, pass through theFourier lens 208, the beam splitter 204, the Fourier filter 210 and thereduction lens 212, and finally reach to the mask blank substrate 216.Mask data 214 is sent to the SLM 206 electronically to set themicro-mirror pixels. The reflected light produce bright spots on themask blank substrate 216, or otherwise absence of reflected light wouldproduce dark spots on the mask blank substrate 216. By controlling andcomposing the reflections, mask, data patterns can be transferred to themask blank substrate 216.

Note that for this type of exposure tool configuration, the illuminationlight path is folded in order to illuminate the SLM at a right angleincidence. This folded illumination path makes a “T” joint to theexposure imaging path. In addition to high power illumination source,this type of exposure system requires using projection lens with highreduction ratio in order to write mask pattern in high accuracy andprecision. Typically, the lens reduction ratio is about 100 times. Usingsuch a high reduction ratio of lens makes the exposure field very smallwith a single SLM die. The physical die size for SLM is in theneighborhood of 1 cm. After a 100-times reduction, the SLM writing fieldis reduced to around 100 microns. This writing field size is very smalland therefore slow when attempting to write a full G8 FPD mask.

Another conventional approach is to use multiple laser beams toilluminate the SLM in succession. The multiple beams are generated byreflecting a single illumination laser source from multi-faced rotatingmirrors. Multiple illumination beams speed up mask writing as they makemultiple exposures at a given time. With this configuration, in oneinstance, the time for writing a G8 FPD mask takes nearly twenty hours.Such a long write time makes machine control expensive to sustain bothmechanically and electronically, hence increases the cost of the FPDmask produced. Using the same exposure tool for the upcoming G10 orbeyond, the cost of manufacturing FPD masks will be even higher.

In another conventional approach, to address the mask cost issue for lowvolume prototyping application, one exposure tool configuration is tomake use of transparent SLM as the mask. This is done such that the maskpattern can be read into SLM to show desired mask patterns without theneed to make a real physical mask. The function of such a transparentSLM mask takes place of the real mask. This saves the mask cost. Fromthe exposure tool configuration perspective, this method is essentiallythe same as the mask-based projection system. Unfortunately, the SLMmask has lower image quality as compared to the image quality on anactual mask. It does not meet the pattern specification requirements forFPD manufacturing.

In yet another conventional approach, a process for roll-to-rollmanufacture of a display by synchronized photolithographic exposure on asubstrate web is described in U.S. Pat. No. 6,906,779 (the '779 patent).The '779 patent teaches a method to expose mask pattern on a roll ofsubstrate. In addition, another conventional method for doingroll-to-roll lithography is described in the article “High-SpeedRoll-to-Toll Nanoimprint Lithography on Flexible Plastic Substrates” bySe Hyun Ahn, etc., Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim; AdvancedMaterials 2008, 20, page 2044-2049 (the Ahn article).

However, in both conventional methods described above, the mask islimited to a predetermined physical size, and the physical maskdimension essentially limits the dimension of the flexible display thatcan be manufactured. Another problem with the conventional methodsdescribed by the 779 patent and the Ahn article is that, to achieve areasonable printing result, the roll of substrate must be stretched flatduring the exposure stage. As a result, the surface flatness of thesubstrate is not as good as rigid glass substrate, typically used forLCD TV display. With such a mask-based lithography, the depth of focus(DOF) is limited due to uneven substrate surface. Thus, it can be verychallenging for these conventional methods to pattern TFT featurecritical dimension (CD) at 5 μm or less. To achieve decent definitiondisplay based on TFT, it is necessary to have CD for TFT mask pattern inthe neighborhood of 3 μm.

The challenges discussed previously for the manufacturing of futuregenerations of FPDs are driven by the need for cost reduction for theFPD industry. One key motivation is to achieve cost efficiency when thenewer manufacturing generation is being adopted. Lithography processrequires maintaining throughput efficiency while assuring product yieldbetter than previous generations. This demands wider lithography processwindow and fewer process defects while contending with bigger FPDsubstrates. As discussed above, there are numerous shortcomings with theexisting exposure tool configurations. One of the major shortcomings isassociated with the use of a mask. The size of the mask is too large tobe manufactured cost effectively. This shortcoming continues to grow asthe size of the mask must increase in order to keep up with futuregenerations of FPDs. Therefore, there is a need for an improved imagingwriter system that addresses the issues of the conventional tools andapproaches.

SUMMARY

The present invention relates to systems and methods for applying maskdata patterns to substrate in a lithography manufacturing process. Inone embodiment, the method includes providing a parallel imaging writersystem having a plurality of spatial light modulator (SLM) imaging unitsarranged in one or more parallel arrays, receiving a mask data patternto be written to a substrate, processing the mask data pattern to form aplurality of partitioned mask data patterns corresponding to differentareas of the substrate, identifying objects in an area of the substrateto be imaged by corresponding SLMs, selecting evaluation points alongedges of the objects, configuring the parallel imaging writer system toimage the objects using the evaluations points, and performing multipleexposures to image the objects in the area of the substrate bycontrolling the plurality of SLMs to write the plurality of partitionedmask data patterns in parallel.

In another embodiment, a system for processing image data in alithography manufacturing process includes a parallel imaging writersystem having a plurality of spatial light modulator (SLM) imaging unitsarranged in one or more parallel arrays. The system further includes acontroller configured to control the plurality of SLM imaging units,wherein the controller includes logic for receiving a mask data patternto be written to a substrate, logic for processing the mask data patternto form a plurality of partitioned mask data patterns corresponding todifferent areas of the substrate, logic for identifying one or moreobjects in an area of the substrate to be imaged by corresponding SLMs,logic for selecting evaluation points along edges of the one or moreobjects, logic for configuring the parallel imaging writer system toimage the one or more objects using the evaluations points, and logicfor performing multiple exposures to image the one or more objects inthe area of the substrate by controlling the plurality of SLMs to writethe plurality of partitioned mask data patterns in parallel.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned features and advantages of the invention, as well asadditional features and advantages thereof; will be more clearlyunderstandable after reading detailed descriptions of embodiments of theinvention in conjunction with the following drawings.

FIG. 1 illustrates a conventional configuration of projection exposuretool used for scanning mask patterns onto FPD substrate.

FIG. 2 illustrates a conventional mask making exposure toolconfiguration.

FIG. 3 illustrates an exemplary digital micro-mirror device according toembodiments of the present invention.

FIG. 4 illustrates a DMD-based projection system according toembodiments of the present invention.

FIG. 5 illustrates an exemplary specular state and diffraction state ofa grating light valve (GLV) device according to embodiments of thepresent invention.

FIG. 6 illustrates an example of a compact SLM imaging unit according toembodiments of the present invention.

FIG. 7 illustrates an exemplary parallel array of SLM imaging unitsaccording to embodiments of the present invention.

FIG. 8 illustrates the corresponding top-down view of the parallel arrayof SLM imaging units of FIG. 7 according to embodiments of the presentinvention.

FIG. 9 illustrates a comparison of a conventional single lens projectionsystem versus the localized process window optimization using thearrayed imaging system according to embodiments of the presentinvention.

FIG. 10 illustrates a method for optimizing localized unevenness insubstrate according to embodiments of the present invention.

FIG. 11 illustrates an application of a mask data structure according toembodiments of the present invention.

FIG. 12 illustrates a method of parallel array voting exposuresaccording to embodiments of the present invention.

FIG. 13 illustrates a method for implementing redundancy in the imagingwriter system according to embodiments of the present invention.

FIG. 14 illustrates the Keystone border blending method according toembodiments of the present invention.

FIG. 15 illustrates a method for placing SLM imaging units in an arrayaccording to embodiment of the present invention.

FIG. 16 illustrates an exemplary implementation of a maskless imagingwriter system for making flexible display according to embodiments ofthe present invention.

FIG. 17 illustrates a SLM imaging unit according to embodiments of thepresent invention.

FIG. 18 illustrates a method of using a linear array of SLM imagingunits for roll-to-roll maskless lithography according to embodiments ofthe present invention.

FIG. 19 illustrates a method of using a two dimensional array of SLMimaging units for roll-to-roll maskless lithography according toembodiments of the present invention.

FIG. 20 illustrates a method of imaging plurality of substrate sizesusing maskless lithography according to embodiments of the presentinvention.

FIG. 21 illustrates a method for positioning each SLM imaging unitcorresponding to conditions of localized substrate surface according toembodiments of the present invention.

FIG. 22 illustrates a method for detecting focus of pixels according toembodiment of the present invention.

FIGS. 23 a-23 c illustrate exemplary apparatuses for detecting focus ofa SLM imaging unit on-the-fly according to embodiments of the presentinvention.

FIG. 24 illustrates an exemplary imaging pattern where pixel votingexposure may be applied according to embodiments of the presentinvention.

FIG. 25 illustrates a method for improving DOF through pixel votingexposures according to embodiments of the present invention.

FIGS. 26 a-26 b illustrate methods to stitch adjacent imaging areasusing an overlapping region according to embodiments of the presentinvention.

FIGS. 27 a-27 d illustrate methods to select paths for stitchingadjacent imaging areas according to embodiments of the presentinvention.

FIGS. 28 a-28 b illustrate methods to stitch a segment of adjacentimaging areas according to embodiments of the present invention.

FIGS. 29 a-29 b illustrate other methods to stitch a segment of adjacentimaging areas according to embodiments of the present invention.

FIGS. 30 a-30 d illustrate methods for imaging an object according toembodiments of the present invention.

FIGS. 31 a-31 b illustrate methods for computing the accumulated dosagefor evaluation points according to embodiments of the present invention.

FIG. 32 illustrates methods for imaging objects by processing a group ofevaluation points according to embodiments of the present invention.

FIGS. 33 a-33 d illustrate methods for optimizing imaging objectsaccording to embodiments of the present invention.

FIG. 34 illustrates methods for making corrections to the opticalimaging writer system according to embodiments of the present invention.

Like numbers are used throughout the specification.

DESCRIPTION OF EMBODIMENTS

System and method are provided for applying mask data patterns tosubstrate in a lithography manufacturing process. The followingdescriptions are presented to enable any person skilled in the art tomake and use the invention. Descriptions of specific embodiments andapplications are provided only as examples. Various modifications andcombinations of the examples described herein will be readily apparentto those skilled in the art, and the general principles defined hereinmay be applied to other examples and applications without departing fromthe spirit and scope of the invention. Thus, the present invention isnot intended to be limited to the examples described and shown, but isto be accorded the widest scope consistent with the principles andfeatures disclosed herein.

Some portions of the detailed description that follows are presented interms of flowcharts, logic blocks, and other symbolic representations ofoperations on information that can be performed on a computer system. Aprocedure, computer-executed step, logic block, process, etc., is hereconceived to be a self-consistent sequence of one or more steps orinstructions leading to a desired result. The steps are those utilizingphysical manipulations of physical quantities. These quantities can takethe form of electrical, magnetic, or radio signals capable of beingstored, transferred, combined, compared, and otherwise manipulated in acomputer system. These signals may be referred to at times as bits,values, elements, symbols, characters, terms, numbers, or the like. Eachstep may be performed by hardware, software, firmware, or combinationsthereof.

Embodiments of the present invention use spatial light modulator (SLM)based image project devices. Two types of SLM based image projection maybe used, one is the digital micro-mirror device (DMD) and the other isthe grating light valve (GLV). Both types of devices may be produced byusing micro-electro-mechanical (MEM) manufacturing methods.

FIG. 3 illustrates an exemplary digital micro-mirror device according toembodiments of the present invention. In this example, a single DMD dieis represented by numeral 302 and an enlarged and simplified view of thesame DMD die is represented by numeral 304. DMD can be addressed bytilting micro-mirrors in fixed angles, typically around ±10° or ±12°, toact as spatial light modulator (SLM). The mirror surface of DMD ishighly reflective to the incident illumination. Each micro-mirror can bemanipulated to tilt (represented by numeral 306) or left un-changed(represented by numeral 308) by the transistor controller underneath. Inone implementation, DMD may have pitch dimension of about 14 μm withabout 1 μm space between each micro-mirror. The pixel count on a singleDMD die may be 1920×1080 mirror pixels, compatible to high definitiontelevision (HDTV) display specifications.

FIG. 4 illustrates a DMD-based projection system according toembodiments of the present invention. In this example, the micro-mirrorhas three states: 1) “On” State 402 at about +10° tilting angle, 2)“Flat” State 404 at no tilt, and 3) “Off” State 406 at about −10°tilting angle. When a ray of light beams shine from a light source 408located at −20° angle to the DMD, they can reflect light beams directlyto pass through projection lens 410 to form bright spots on the displaysubstrate, for the mirrors that are at “On” State or “1” in binary. Formirrors that are at “Flat” State and “Off” State, or the “0”, the lightbeams reflected in an angle falling outside of the collection cone ofthe projection lens, at approximately −20° and −40° respectively. Henceno light pass though from those mirror sites, dark spots are then formedon the display substrate. Since each of micro-mirror reflection cannotbe visually resolvable by human eyes, a gray shade can be constructed bycombining a group of light and dark spot pixels in a ratio whenprojected. This method enables the projection of realistic images withmillion shades of grays and colors.

Note that the higher diffraction orders of diffraction beam from the“Flat” State and the 2^(nd) order of diffraction beam from the “Off”State can still fall within the collection cone angle of the projectionlens. This may create unwanted flare that reduces the desire imagecontrast. According to embodiments of the present invention, a preciselyaimed and focused high intensity illumination source may be used toincrease the pixel diffraction efficiency to optimize the design of theprojection optics using DMD for imaging writer.

According to other embodiments of the present invention, GLV is anotherapproach for implementing image projection. The top layer of GLV deviceis a linear array of materials, also referred to as ribbons, which arehighly reflective. In one embodiment, ribbons may be 100-1000 μm long,1-10 μm wide and closely spaced by 0.5 μm. The imaging mechanism of GLVis essentially addressable dynamic diffraction grating. It functions asa phase modulator. A GLV device may include a group of six alternativeribbons deflected to form dynamic diffraction grating.

FIG. 5 illustrates an exemplary specular state and diffraction state ofa GLV device according to embodiments of the present invention. When theGLV ribbons (in cross-sectional view) are co-planar (represented bynumeral 502), the incident light is reflected specularly, i.e. all inthe 0^(th) diffraction order. When incident light shines on a group ofribbons, where ribbons are deflected in an alternating fashion(represented by numeral 504), a diffraction pattern is formed withstrong orders but with suppressed 0^(th) order. A high contrastreflection image can be constructed by filtering out either 0^(th) or±1^(st) orders. That is, no image may be formed if to re-capture all of0^(th) or ±1^(st) orders in the objective lens. Unlike DMD, the entireimage in a field of view as formed by GLV is based on scanning line byline since there may be one line of diffraction images are formed by thelinear array of grating ribbons at one time.

As discussed in association with FIG. 1 and FIG. 2, in order to achievethe throughput requirements, high powered illumination sources for theconventional systems are necessary. In one example, high pressure Hgshort-arc lamp in the kilo-Watts range is used. Another example is touse high powered Excimer laser. Due to the use of high powerillumination sources, the illumination light path needs to be directedfrom a distance to reduce the heat generated and then be folded for aright illumination. This type of configuration separates theillumination and SLM imaging system into two separate units and thelight path and the lens are perpendicular to each other.

To address the limitation of the conventional systems and approaches,the improved exposure tool configuration reduces the need to usehigh-powered illumination sources. An in-line imaging system isconfigured where each of the imaging unit includes the SLM, theillumination sources, the alignment illumination, the electroniccontrol, and the imaging lens. This system may have a lower exposurethroughput when using low powered LED and diode laser illuminationsources. However, the exposure throughput may be increased by using alarger number of imaging units. One of the benefits of using a compactSLM imaging unit is that a scalable array of such units may be packedfor different imaging applications. In one application example, whenarrayed with more than 1000 such compact SLM imaging units, the writingthroughput exceeds the existing multi-wavelength, mask-based exposuretool configuration.

FIG. 6 illustrates an example of a compact SLM imaging unit according toembodiments of the present invention. In this example, the compact SLMimaging unit includes a spatial light modulator 602, a set ofmicro-mirrors 604, one or more illumination sources 606, one or morealignment light sources 608, and a projection lens 610. The illuminationsource 606 may be implemented with LED or diode laser having wavelengthless than 450 nm with blue light or near UV. The alignment light source608 may be implemented with a non-actinic laser source or LED forthrough-the-lens focus and alignment adjustment. The projection lens 610may be implemented with a lens having a 5× or 10× reduction. As shown inFIG. 6, the illumination sources 606 and the alignment light source 608are all placed outside of the collection cone angle of the projectionlens. In this exemplary implementation, off-the-shelf projection lenseswith numerical aperture NA of 0.25 at resolving power of about 1 μm maybe used. The relatively low NA ensures better depth of focus (DOF). Inone lithography process example, using NA of 0.25 for 1 μm photo resistCD target, the DOF may be >5.0 μm. The resolution and DOF calculationsare based on Rayleigh criterion:

Minimum feature resolution=k ₁(λ/NA)

DOF=k ₂(λ/NA²)

where, k₁ and k₂ are process capability factors. According to animplementation of lithography manufacturing process based on Novolakchemistry photoresist, k₁ is in the range from 0.5 to 0.7, k₂ is from0.7 to 0.9, and λ refers to the exposure wavelength.

In order to fit a compact form factor, illumination sources may be blue,near UV LED, or semiconductor diode laser. To get sufficient intensity,in one design example, the illumination sources are placed close to theSLM surface and there may be multiple illumination sources placedsurrounding the SLM. The SLM may be DMD or GLV with proper optical lensdesign matched to each. In one example, the targeted intensity level atthe substrate may be between 10-100 mW per square centimeter of theactinic exposure wavelength.

In this exposure tool configuration example, the housing for theelectronic control boards for each compact imaging system conforms to aspecified compact factor. It is located on the top of the SLM, away fromthe illumination sources. This facilitates ventilation and heatdissipation. The physical dimension for a single compact SLM imagingunit depends on the required imaging performance and the availablecomponents use off-the-shelf supply, such as the projection lens, LED ordiode laser illumination sources, and focus/alignment diode laser, eachwith required room for heat dissipation. Another approach is to havecustom design for the components so that the physical dimension for asingle SLM imaging unit can be trimmed to an even more compact form. Acustom designed SLM imaging unit may have a dimension of approximately 5cm×5 cm in 2D cross-section compared to a dimension of approximately 10cm×10 cm using off-the-shelf supply.

For the G10 FPD manufacturing, a typical substrate size is 2880 mm×3130mm. Using the physical dimension of compact SLM imaging lens, a systemmay include hundreds of compact SLM imaging units arranged into an arrayof parallel imaging units. FIG. 7 illustrates an exemplary parallelarray of SLM imaging units according to embodiments of the presentinvention. In this example, the image writing can be performed by 600 to2400 parallel arrays of SLM imaging units (702, 704, 706, 708, etc.)simultaneously and each parallel array may includes multiple SLM imagingunits.

According to embodiments of the present invention, the exposurethroughput may be determined using a known example throughput of a SLMmask writer, such as 20 hours for the mask size of 1300 mm×1500 mm, maybe used as a starting point. Throughput depends on the intensity levelat the substrate plane. In this approach, for the intensity level of 50mW per square centimeter, achievable with LED or diode laser sources,and for the nominal exposure energy of 30 mJ/sq-cm-sec, the exposuretime is approximately 0.6 seconds. In another approach, where theexposure tool uses high-powered illumination source, the intensity levelat the substrate is at least 200 mW per square centimeter or higher. Thethroughput for such a mask-based stepper/scanner system is about 50 G8FPD substrate plates per hour. By taking into account of bothhigh-powered and low-powered illumination sources, the throughputestimation in one example is from 25 to 100 substrates per hour,depending on the density of parallel SLM imaging units used in thearray. This shows that such an array parallel exposure configuration iscompetitive economically.

FIG. 8 illustrates the corresponding top-down view of the parallel arrayof SLM imaging units of FIG. 7 according to embodiments of the presentinvention. In this example, each row or column may represent a parallelarray of SLM imaging units, and each parallel array may include multipleSLM imaging units 802. Lithography manufacturing yield is directlyrelated to process window. Here process window refers to the range focussettings in conjunction with the range of exposure dose settings thatcan print feature CDs within the specifications. That is, for a morerobust process window, it can tolerate wider defocus settings and/orexposure dose settings. A wider process window may produce a betterproduct yield. With bigger substrate for each newer generation,lithography window becomes smaller. This is mainly due to the moretendencies for larger and thinner substrate material to warp or sag. Toaddress this issue, the solution calls for tightening thickness andsurface uniformity specifications for substrate material. For mask-basedexposure tool, maintaining uniformity and focus control over an exposurefield that is larger than about two meters in one side is not only veryexpensive but also technologically challenging. To assure a workableprocess window, exposure tool need to be able to optimize focus andillumination in both local and global fashions.

As shown in FIG. 8, this array parallel exposure system addresses theissues discussed above. This is because each of the compact SLIM imagingunits can be optimized locally for better illumination and focuscorresponding to its own exposure area. That ensures a better processwindow in each exposure area of the SLM imaging unit. The entire processwindow is then improved globally using optimized contributions from theSLM imaging units.

FIG. 9 illustrates a comparison of a conventional single lens projectionsystem versus the localized process window optimization using thearrayed imaging system according to embodiments of the presentinvention. On the left hand side of FIG. 9, the conventional single lensprojection system 902 must be tuned to a compromised focal plane 904, asshown in dotted line. The solid line 906 represents the actual surfacecontour of the substrate in cross-sectional view. The double arrow 908indicates the best focus setting corresponding to a single lens that isused to image the pattern. The lines with round heads 910 represent themaximum contour range correspond to each imaging lens and the dot-dashedlines indicate the upper and lower limits of the focus range.

As shown in FIG. 9, for the conventional single lens projection system,the large-sized substrate curvature may have already exceeded the focusrange of the lens. The center of focus may be only marginally acceptablewith respect to both of the peak and valley curvatures in the substrate.The overall process window becomes limited. On the other hand, the righthand side of FIG. 9 shows an improved projection system with imagingunits arranged in an array. The focus 914 of an imaging unit 912 can betuned individually for each localized area covered. As a result, eachfocus setting can be placed well within the focus control limits asrepresented by the lines 916. In addition to the ability to fine tunefocus in each of the local area covered, the illumination of eachimaging unit may also be adjusted to achieve a better uniformitycompared to the adjustment may be performed by a single lens system.Therefore, a more robust process window is achieved by using the arrayedimaging unit system.

FIG. 10 illustrates a method for optimizing localized unevenness insubstrate according to embodiments of the present invention. In thisexample, region of uneven contours are detected in the substrate asindicated by numeral 1002. One method of tuning optimization is to applya focus averaging scheme for the uneven local exposure areas that areassociated with a SLM imaging unit as well as the surrounding areasassociated with SLM imaging units in the neighborhood of the SLM imagingunit of interest. The more imaging units in the neighborhood of theuneven areas that can be included for averaging, the better globalizedoptimization can be achieved. A person skilled in the art wouldappreciate that other averaging techniques may be applied to thedisclosed imaging system for the entire substrate plate to achieve amore uniform image globally across the whole substrate.

In one implementation, the mask data format for thin film transistor(TFT) based LCD display may be implemented as follows. Note that thehierarchical stream data format GDSII may be used for taping out maskdata, but this type of mask data format may not be well-suited for thisparallel SLM imaging system. To convert from hierarchal mask data toflat format, this can be done by using an off-the-shelf CAD softwareprogram. However, after flattened the mask data, further processing themask data is needed. Mask data structure is used in conjunction with thearrayed parallel imaging writer system to produce higher quality images.

For the arrayed parallel imaging writer system, the mask data structuremay be flattened and may be partitioned into pieces of a predefined sizeto properly or evenly feed to every SLM imaging unit. The mask datastructure includes information that indicates the placement for eachpiece of mask data relative to its respective imaging unit. Moreover,the mask data structure includes information that specifies how featuresthat span multiple imaging units will be divided among them. The dataplacement tuning can be recognized via the mask data structure that isrelated to the adjacent mask data areas from the adjacent imaging units.

FIG. 11 illustrates an application of a mask data structure according toembodiments of the present invention. In this example, a hierarchicaldescription of a mask data in terms of multiple levels of mask datainstances 1102 is first flattened to form a flattened mask data 1104.Then, the flattened mask data 1104 is partitioned into multiplepartitioned mask data patterns. One such partitioned mask data patternis shown as a shaded area 1106, which is also shown as the center blockin the nine blocks (separated by dotted lines) at the bottom of FIG. 11.Sufficient mask patterning overlaps between the adjacent imaging units,shown as horizontal and vertical strips 1108, are needed to ensureuniform pattern blending around the borders, where each block representsa partitioned mask data to be imaged by one or more SLM imaging units.According to embodiments of the present invention, the partitioned maskdata includes a first set of identifiers for identifying run-inconditions of mirror pixels within a SLM imaging unit and a second setof identifiers for identifying run-out conditions of mirror pixelswithin a SLM imaging unit. A run-in condition occurs where excessivepixels are found in an area between two SLM imaging units. A run-outcondition occurs where insufficient pixels are found in an area betweentwo SLM imaging units. Each partitioned mask data pattern is fed to itscorresponding SLM imaging unit for processing, where each SLM imagingunit writes its associated partitioned mask data pattern inpredetermined overlapped areas using adjacent SLM imaging units asreferences to ensure the imaging blending and uniformity meet designcriteria. The partitioned mask data pattern may be optimized to enableparallel voting exposures for feature CD uniformity. In this case, aparallel voting exposure scheme is used in minimizing processingvariables that may negatively impact CD uniformity. The elimination ofGaussian speckles due to the use of diode laser is accomplished by usingsufficient number of micro-mirror pixel exposures for voting.

FIG. 12 illustrates a method of parallel array voting exposuresaccording to embodiments of the present invention. The method firstsends the mask data to each of SLM imaging unit in a row-by-row fashion,then to flash the row of micro-mirror pixels starting from one end ofthe row to the next until reaching the opposite end. In one example, themethod starts with block 1201 and flashes the bottom row of micro-mirrorpixels. It then moves block 1202 and flashes the second row from thebottom row of micro-mirror pixels. In block 1203, the third row from thebottom row of micro-mirror pixels is flashed. The method continuesthrough blocks 1204, 1205, 1206, 1207 and flashes the corresponding rowof micro-mirror pixels. And in block 1208, the method has traversed thelast row of micro-mirror pixels (which is the top row) in thisparticular example. The same walking-row of micro-mirror pixels loopsagain and again from the start to the end. The looping of thewalking-row corresponds to exposure actions for writing patterns onsubstrate. Because micro-mirror flashing rate is fast enough, thefeature patterns are exposed by the fast moving walking-row numeroustimes until nominal exposures level is accumulated. Thus, such a patternwriting scheme is, in effect, done by voted exposures from numerousmicro-mirror pixels. By moving substrate stage in a coordinated pace andorientation, the writing for entire substrate is carried out with thesame voting exposure scheme.

The walking-row approach illustrated in FIG. 12 is one example oflooping walking-row for making one style of parallel voting exposurelocally or sub-locally for every imaging unit. In other embodiments,looping methods based on column or diagonal row/column may be used foreffective parallel voting exposures. Additional voting schemes can bederived such as interlaced walking-rows from the two adjacent SLMimaging units or to use multiple walking orientations with several datarows, etc., may be employed to improve printing performance, althoughpossibly at the expense of additional stage motion.

For array parallel exposure under heavy production environment,redundancy or fault-tolerance may be built-in to prevent production flowfrom interruption. That is, as the exposure control routine detects afailure of an SLM imaging unit, it then takes action to disable theproblematic imaging unit, redistributes the mask data to one or more ofthe adjacent imaging units, and then has these adjacent imaging unitscomplete the exposure tasks before unloading the exposed plate. Thiscorrective exposure routine continues until the full batch-load ofplates is done. The process continues until both the imaging performanceand throughput hit are considered acceptable.

FIG. 13 illustrates a method for implementing redundancy in the imagingwriter system according to embodiments of the present invention. In thisexample, after detecting that image unit 212 has malfunctioned, thisunit is shut down. One of the 8 adjacent imaging units may be selectedto take over. In this case, the writing for the unit 212 area is doneafter exposures of other areas have been accomplished.

Micro mismatched (local to local) borders from the two adjacent SLMimaging units can occur when imaging distortions result from substratewarping or sagging. This is represented by numeral 1402, where datapatterns fall outside of the boxed area. In this case, the patternblending in the overlapped areas needs to be optimized. FIG. 14illustrates the Keystone border blending method according to embodimentsof the present invention. As shown in FIG. 14, the method turns onmicro-mirror pixels at the selected border end 1404 that allows betteroverlap matching to the adjacent imaging unit writing area 1406. Personsskilled in the art would appreciate that other approaches may be used toachieve border blending by turning on micro-mirror pixels selectively atdesired sites.

According to some embodiments, blending may be performed by turning onselected micro-mirror pixels in alternate or complementary mannerbetween the adjacent overlapping borders. According to yet some otherembodiments of the present invention, mixing walking-row exposure votingaction together with additional pixel turning at selected sites may beused to achieve better blending.

In order to achieve the intended alignment accuracy and precision forthe array parallel imaging system, the method decomposes the alignmentscheme into several accuracy precision levels in cascade. Firstalignment level is to aim for global alignment accuracy level, next isto narrow into intermediate level of accuracy precision. Using thisbottom-up approach, the method achieves the desired accuracy precisionlevel.

In one approach, three accuracy precision levels are defined: the unitlens array placement, the lens center tuning, and the micro-mirrorimaging data manipulation. FIG. 15 illustrates a method for placing SLMimaging units in an array according to embodiment of the presentinvention. This method provides global placement accuracy of the SLMimaging units 1502 in the millimeters range. Next, for each SLM imagingunit, the position of projection lens assembly is electronically tunedto precision in micrometer range. This is done by aligning the lenscenter using HeNe laser (or other non-actinic alignment light source) toa known reference position on the stage. Finally the micro-mirrors arecontrolled to achieve alignment requirements in precision of nanometerrange.

According to embodiments of the present invention, the alignment processfor making exposure may be carried out as follows:

1) Using a known reference site on the stage, the lens center for eachSLM imaging unit in the array is first calibrated. This allowsconstructing a mathematical grid array points in reference to thephysical lens array.2) For the first masking layer, when there is no alignment marksprinted, the plate alignment is done mechanically relying mainly on thestage precision.3) When the substrate plate has alignment marks throughout the plate asprinted from the previous masking layer, these alignment marks can bedetected by the corresponding SLM imaging units. From this, a grid mapis constructed in reference to the actual image locations that are onthe substrate plate.4) By comparing the two grid maps (SLM imaging unit vs. printedalignment marks detected from the substrate), build a grid map matchingmathematical model for stage travel guide.5) In one example, by considering 2400 array SLM imaging units for G10substrate, the maximum stage travel distance is about 120 mm in eitherhorizontal (X) or vertical (Y) direction. This is included for grid mapmatching calculation. Note that such a stage travel distance is rathersmall hence technologically advantageous compared to making the stagetravels in full plate width and length required by using mask-basedexposure tool for the G10. The G10 plate substrate can have a heavymass. The shorter stage distance traveled while carrying such a heavymass, the better system accuracy performance may be achieved.6) To fine-tune sub-micron alignment accuracy, the method embeds thecorrection factors into the mask data that is being sent to thecorresponding imaging unit. That is, the correction factors for everyimaging unit may be different depending on the relative imaginglocations on the substrate. They can also be different from plate toplate since the substrate warping condition may be different and may bedetected ahead of the time before exposing each plate.

FIG. 16 illustrates an exemplary implementation of a maskless imagingwriter system for making flexible display according to embodiments ofthe present invention. As shown in FIG. 16 the maskless image writersystem 1600 is formed by one or more arrays of SLM imaging units, where1602 is an example of one of the SLM imaging units. The one or morearrays of SLM imaging units may be formed into a particular shape, forexample circular, which may be required by a specific application. Inanother exemplary implementation, the maskless imaging writer system maybe configured to make non-flexible displays.

FIG. 17 illustrates a SLM imaging unit according to embodiments of thepresent invention. The SLM imaging unit includes blue and red diodelasers 1702, an aperture 1704, a lens 1706, a spherical mirror 1708, aDMD 1710 mounted on a printed circuit board 1712, a beam dump 1714, abeam splitter 1716, a CCD camera 1718, and a lens assembly 1720. Theblue and red diode lasers 1702 further includes a red laser diode(non-actinic) 1722 and four blue laser diodes (actinic) 1723, 1724, 1725and 1726. The laser diodes may be arranged in the example as shown inFIG. 17. The center red laser diode is non-actinic and it is mainly usedfor alignment or catching for initial focus setting. The four blue laserdiodes are actinic and they are used for making exposure. Depending onthe physical size of the laser diode package, other types of arrangementusing different numbers of laser diodes are possible as long as auniform intensity can be achieved. In another approach, the actinicillumination can also be delivered via optical fiber bundles. In that,each laser diode shines on the one end of the optical fiber bundle andlet fiber carry the actinic light to shine from the other end of theoptical fiber bundle. In other embodiments, LEDs may be used instead ofdiode lasers. In this arrange example, the blue LEDs can be placedtightly together in such a way to achieve uniform intensity whilemultiple red LEDs can be placed in relative locations that may beconfigured to achieve alignment and initial focusing purposes. In thisexample, the blue and red diode lasers 1702 project light to thespherical mirror 1708 through the aperture 1704 and the lens 1706. Thelight is then reflected from the spherical mirror 1708 to the DMD 1710.According to the state of each mirror in the DMD, the light may be sentto the beam dump 1714, or to a substrate through the lens assembly 1720.The image thus created on the substrate reflects back upward throughlens 1720 and beam splitter 1716 to CCD camera 1718.

FIG. 18 illustrates a method of using a linear array of SLM imagingunits for roll-to-roll maskless lithography according to embodiments ofthe present invention. In this example, the SLM imaging units 1802 arearranged as a single line array as shown in FIG. 18. The substrate 1804may be controlled to move along the direction of substrate movement (theX direction) and the linear array of SLM imaging units 1802 may becontrolled to move back and forth perpendicular to the direction ofsubstrate movement (the Y direction) in the plane of the substrate 1804.The exposure of the linear array of SLM imaging units can be tuned toprocess certain area of the substrate 1804 in synchronization with theroll-to-roll substrate movement. In this way, the linear array of SLMimaging units may be controlled to image a substrate that has physicaldimensions larger than the size of the linear array of SLM imagingunits. Because of the ability to control the SLM imaging units to movein the direction of substrate movement as well as in the directionperpendicular to the substrate movement, the image writer system shownin FIG. 18 overcomes the size limitations of the physical masks requiredin the conventional methods described in the '779 patent and the Ahnarticle.

FIG. 19 illustrates a method of using a two dimensional array of SLMimaging units for roll-to-roll maskless lithography according toembodiments of the present invention. This figure shows a top view of atwo dimensional SLM imaging array 1902, where each circle represents aSLM imaging unit. Similar to the example shown in FIG. 18, the substrate1904 may be controlled to move in the X direction and the twodimensional array of SLM imaging units 1902 may be controlled to moveback and forth in the Y direction in the plane of the substrate 1904.The exposure of the two dimensional array of SLM imaging units can betuned to process certain area of the substrate 1904 in synchronizationwith the roll-to-roll substrate movement. In this way, the twodimensional array of SLM imaging units may be controlled to image asubstrate that has physical dimensions larger than the size of the twodimensional array of SLM imaging units. Thus, the image writer systemshown in FIG. 19 overcomes the size limitations of the physical masksrequired in the conventional methods described in the '779 patent andthe Ahn article. Note that in some embodiments, the two dimensionalarray of SLM imaging units may be formed in a staggered or non-staggeredarray formation.

FIG. 20 illustrates a method of imaging plurality of substrate sizesusing maskless lithography according to embodiments of the presentinvention. Similar to the method described in FIG. 19, the image writersystem also employs a two dimension array of SLM imaging units 2002.Since the two dimensional array of SLM imaging units 2002 may becontrolled to receive and process imaging data automatically in acontinuous fashion, the image writer system can transition from onesubstrate design to a different substrate design by loading a new TFTmask database seamlessly without the need to stop and change to a newmask as required by the conventional methods described in the '779patent and the Ahn article. In the example shown in FIG. 20, differentsized substrate designs, such as 2006, 2008, 2010, 2012, and 2014 can beprocessed on-the-fly as the roll-to-roll substrate containing thedifferent sized substrate designs move by the two dimensional array ofSLM imaging units 2002.

FIG. 21 illustrates a method for positioning each SLM imaging unitcorresponding to conditions of localized substrate surface according toembodiments of the present invention. In this example, the methodexamines the unevenness of the substrate surface 2104 during exposure,and adjusts the linear array of SLM imaging units 2102 accordingly. Inthis example, the uneven substrate 2104 is excessively shown toillustrate the benefit of having optimum height adjustment for each SLMimaging unit. This allows achieving auto-focus tuning to come within therange of DOF for intended resolution CD from 1 to 5 μm. This method isfurther described in the following sections.

In one approach, for printing TFT based photo voltaic (PV) panel, theminimum features CD can be more than 50 μm. In this printing resolutionrange, it often thought that ink-jet printing could be a less costlyoption. However, one major drawback for ink jet printing is defect-pronedue to ink mist, a side effect that comes with ink jet droplet stream.Ink-jet printing is inherently not as clean as lithography process. Itmay be suited for patterning mask features that do not form activedevice or mainly for passive viewing purpose. For production worthy ofmaking active TFT device with roll-to-roll printing, scalable array ofSLM imaging units provides a better solution for maskless lithographybecause it produces better device yield. In this method, a magnificationprojection is used for maskless imaging. That is, instead of using areduction objective lens, the exposure lens of the SLM imaging unitemploys an enlargement objective lens that can magnify product featuresize from 25 μm to a couple of hundred μm in a controlled fashion.

In order to maintain best focus over a substrate that may not beperfectly flat, one way is to monitor and adjust the focus of the SLMimaging unit during exposure. FIG. 22 illustrates a method for detectingfocus of pixels according to embodiments of the present invention. Oneapproach for monitoring focus is to use a through-the-lens monitoringcamera to capturing images of the exposure in progress. After images arecaptured, an analysis of dark-light pixel image captured, in comparisonwith what would be expected for the exposure pattern, can readily derivea relative measure of the amount of defocus. As shown in the example ofFIG. 22 is a pair of light and dark pixels (2202 and 2204) with in-focus(2206 and 2208) and an out-of-focus 2210 conditions. At the boundarytransition from dark to light area, the in-focus pair exhibits a sharpertransition pattern, whereas the out-of-focus pair has a blurredtransition. The degree of blurred transition can be mapped to refer tothe amount of defocus. In other approaches, one may monitor and analyzespatial frequencies in the image. Since focus errors preferentiallyreduce the higher spatial frequencies, one may assess the amount ofdefocus by comparing the loss of high frequency components of the imagecaptured. Yet another method is to monitor and analyze the imagecontrast from a group of light-dark patterns, with image contrast beingthe best at optimum focus setting. And the degrees of contrast lost canbe referred to the amount of de-focus.

Although the methods described above are effective focus monitors of thesize of focus error, they do not directly provide any indication of thedirection of the error. To address this issue, the system may, undersoftware control, constantly vary the focus slightly over a rangecentered on the target focus, and update the target focus position tokeep it at the best focus. This can most sensitively be determined bybalancing the errors at the two extremes of the range. It may beadvantageous, however, to avoid the need to intentionally defocus theexposure image. One way to achieve this is to perturb the focus of thecamera in a controlled fashion, without altering the focus of theexposure image. This can be done on a through-the-lens monitor camera byaltering the effective optical path length between the camera and theobjective lens. To a first order approximation, changing the focallength on the camera side of the lens (f₂ in the diagram) has the sameeffect as changing f₁ by the same percentage. This focus change can beeffected by vibrating the camera in and out, reflecting the image off amirror that vibrates, or as shown in FIG. 23 a, by passing the lightthrough a spinning disk with segments having different thicknessesand/or refractive indices, to give the desired variation in effectiveoptical path length. This is as shown as the first OPD 2316 and thesecond OPD 2326. Similarly, the image could be reflected off a mirroreddisk, with segments at different heights.

FIG. 23 a illustrates an exemplary apparatus for detecting focus of aSLM imaging unit on-the-fly according to embodiments of the presentinvention. As shown in FIG. 23 a, the apparatus includes an imagingsource 2302, a beam splitter 2304, an objective lens 2306 and itshousing 2308. An example of the imaging source 2302 is shown in FIG. 17,including the components 1702 to 1714. The apparatus also includes afirst camera sensor 2310 (also referred to as the camera or sensor forshort), a first motor 2312, a first refractive disk 2314, and a firstoptical path difference (OPD) modifier 2316. The first OPD modifier 2316may be formed from a circular optical device 2317, where the circularoptical device 2317 may be made with multiple sectors (for example 2318)and each sector is made with different refraction index material, ormade with the same refractive index material but with differentthickness than can cause optical path difference.

Another way of determining the focus adjustment direction is to have twocameras that can capture the images from different optical path lengthsas shown in FIGS. 23 b and 23 c. FIGS. 23 b-23 c illustrates two otherexemplary apparatuses for detecting focus of a SLM imaging uniton-the-fly according to embodiments of the present invention. Inaddition to the elements shown in FIG. 23 a, these exemplary apparatusfurther includes a second camera sensor 2322 (also referred to as thecamera or sensor for short), and a second optical path difference (OPD)modifier 2326. FIG. 23 c also includes a third OPD modifier 2330. Thesecond and third OPD modifiers 2326 and 2330 may be formed in a similarfashion as the first OPD modifier 2316. When with two camera sensors2310 and 2322 are used, the two respective OPDs 2316 and 2326 withdifferent refractive indexes can be set up to determine focus adjustmentdirection. In another embodiment, the different OPDs 2316 and 2326 areeffected simply by placing the respective cameras 2310 and 2322 atdifferent physical distances.

The examples shown in FIGS. 23 b-23 c examine the images from firstcamera sensor to second camera sensor to compare and analyze the focusadjustment direction, and adjust focus setting to equalize the defocusobserved in the two camera sensors, thus assuring that the best focus isachieved at an OPD midway between the two camera sensors. Here, thefirst and second camera sensors are configured to observe the substratewith complementary focus offsets to determine direction of a targetfocus. Yet another method is to avoid adjusting focus by moving theobjective lens up and down, this is to place the third OPD 2330 abovethe housing 2308 of the objective lens 2306 to effect the focusadjustment by changing the effective optical path length.

The on-the-fly focus monitor and adjustment may be performed as follows:

-   -   1) The separation of substrate surface from the objective lens        is set within the focusing range.    -   2) To begin with, image is formed and captured by using        non-actinic illumination. This will not cause any damage to the        photo sensitive material for exposure. That is, the initial        focus is set by using non-actinic illumination; the objective is        then adjusted accordingly for best focus.    -   3) As the exposure stage starts to move along the direction of        substrate movement (the X direction), the actinic exposure        starts.    -   4) Image captured is then monitored under the actinic        illumination. The Objective lens is adjusted accordingly.    -   5) Note that each focus adjustment is for the next exposure site        but based on best focus determined for the previous exposure        location.    -   6) The amount of focus adjustment for the objective lens is        based on the optical path difference measured for f1 vs. f2.

As described above, the image writing may be monitored by one or morecameras on-the-fly while exposure is taking place. By using a mirrorpixel voting scheme for exposure, each image pattern is being exposedand formed by many DMD mirror pixels. This exposure scheme inherentlypermits more margin of focusing error at the initial stage of exposuresince each mirror pixel exposure only contributes a small fraction ofthe total exposure energy required. As pixel voting exposure progresses,the focus of each SLM imaging unit may be tuned and adjusted on-the-fly.This margin of focus error is important for writing the features thatare either isolated “hole-like” patterns surrounded by dark field, orisolated “island-like” patterns surrounded by a clear field such as theexample shown in FIG. 24. This is because both aforementioned featurepatterns are not easy to set optimum focus initially due to the lack ofimage variation while perturbing the focus setting. However, the optimumfocus can be determined after a number of exposures have beenprogressed.

In another approach, the type of auto-focusing mechanism described abovemay be used to accomplish “focus voting exposure” to expand the overallDOF. FIG. 25 illustrates a method for improving DOF through pixel votingexposures according to embodiments of the present invention. In theexample shown in FIG. 25, the optimum exposure setting can bedynamically tuned during the pixel voting exposure. This allows thepixel voting exposures to be accomplished by a different best focuslevels that are still within the DOF. This scheme enables the finalimage pattern to be exposed and formed by many votes of the focussettings 2502 that may extend to the overall resultant DOF 2504.

FIGS. 26 a-26 b illustrate methods to stitch adjacent imaging areasusing an overlapping region according to embodiments of the presentinvention. FIG. 26 a illustrates two adjacent imaging areas 2602 and2606, and their corresponding SLMs 2604 and 2608, respectively. Anoverlap region 2610 is defined as the area between the two adjacentimaging areas 2602 and 2606, where the SLM 2604 may image across atheoretical boundary 2612 to a user defined boundary 2614 (dotted line)in the imaging area 2606. Similarly, the SLM 2608 may image across thetheoretical boundary 2612 to another user defined boundary 2616 (dottedline) in the imaging area 2602. By having this double coverage in theoverlapping area 2610, the method may compensate for inconsistencies,such as positional mismatches or exposure dose differences, from onearea to the other, and vice versa.

FIG. 26 b illustrates another two adjacent imaging areas 2622 and 2626,and their corresponding SLMs 2624 and 2628, respectively. In thisexample, the two SLMs and their corresponding imaging areas arehorizontal to each other, as opposed to be vertical to each other asshown in the example of FIG. 26 a. Although the orientation of theoverlapping region may be different between FIG. 26 a and FIG. 26 b,similar technique may still be applied to both cases, or in otherembodiments, horizontal overlapping regions may be treated differentlyfrom the vertical overlapping regions. Similar to FIG. 26 a, an overlapregion 2630 is defined as the area between the two adjacent imagingareas 2622 and 2626, where the SLM 2624 may image across a theoreticalboundary 2632 to a user defined boundary 2634 (dotted line) in theimaging area 2626. Similarly, the SLIM 2628 may image across thetheoretical boundary 2632 to another user defined boundary 2636 (dottedline) in the imaging area 2622.

One approach to image the overlapping region 2630 is to have the twoSLMs 2624 and 2628 to fade over each other. The lines 2638 and 2639(dotted line) show the approximate conception intensity of the SLMs 2624and 2628 respectively. In the overlapping region 2630, the intensity ofSLM 2624 transitions from full intensity to zero intensity while theintensity of SLM 2628 transitions from zero intensity to full intensity.It is noted that for this approach, if the theoretical boundary issubstantially aligned (for example, within 50 nm) with the actualtransition of the imaging area, good imaging results may be expected.However, if the theoretical boundary is not substantially aligned withthe actual transition of the imaging areas, such as the transitions fallwithin certain narrow structures or edges of structures, less thandesirable imaging profiles are observed. This issue may be addressed bythe methods described in association with FIGS. 28 and 29 below.

FIGS. 27 a-27 d illustrate methods to select paths for stitchingadjacent imaging areas according to embodiments of the presentinvention. In many applications, such as flat panel display andintegrated circuit fabrication, the structures 2702 and the gaps betweenthem often have much different sizes, and the smaller of the two istypically more critical. In the following description, large structures2702 with small gaps between them are shown, but person skilled in theart would appreciate that the reverse situation of small structureseparated by large gaps may employ similar techniques described herein.If a method simply selects a stitching path anywhere in the overlappingregion, a number of problems may arise as shown in FIG. 27 a. In theexample shown in FIG. 27 a, the line segments A′B′ 2704 or C′D′ 2706,which are blindly selected without a detailed analysis of thestructures, as a result, the stitching path are too close to edges ofthe structure 2702, which may lead to errors such as marginal resolutionand/or increased processing time and data associated with the stitchingpaths A′B″ 2704 and C′D′ 2706. Instead, a better approach to obtain astitching path is shown in FIG. 27 b, where the stitching path consistsof line segments AB 2708, BC 2710, CD 2712, DE 2714, and EF 2716 passthrough the middle (or wider area) of the structures 2702 such that ittries to avoid being closes to edges as much as possible and passesdirectly across narrow gaps such as the line segment BC 2710. In thisway, it reduces errors, processing time and data for the stitching pathpass through the structures 2702.

FIG. 27 c illustrates two examples that should be avoided in creating astitching path through different structures 2720 and 2722. For the linesegment E′F′ 2724, it passes through the very narrow structure 2722 (orthin lines), meanwhile the line segment G′H′ 2726, passes throughstructures 2720 and 2722 diagonally. Both line segments E′F′ 2724 andG′H′ 2726 have left behind some very difficult shapes and edges forsubsequent processing. In some situations, the lines have changed thewidth of the structures by a large fraction, which in turn leads toerrors, and increased computational time and data associated withprocessing such difficult shapes and structures. A preferred approachfor generating a stitching path is shown in FIG. 27 d, where the linesegments I-J-K-L 2728 passes through the structures 2720 and 2722cleanly, which would result in less errors, and reduced computationaltime and data for processing the stitching path shown in FIG. 27 d.

Note that in the following sections, two cost functions are introducedto address the issue associated with FIG. 27 a and FIG. 27 c, the firstcost function is related to the proximity to an edge of a structure, andthe second cost function is related to the width of a structure for astitching path to pass through. Also note that, human eyes tend to pickup image processing artifacts, such as straight lines, much easier thannon-straight lines. Other approaches for creating stitching paths aredescribed. Since the disclosed optical imaging writer system conductsimaging processing in a maskless manner, a stitching path that traversesthrough the overlapping region in a random fashion may be created, whichis infeasible for conventional imaging system with fixed masks andlenses. Choosing a stitching path that passes through large, simplefigures and gaps reduces the measurable effects of mismatches betweenadjacent imaging areas, and choosing a stitching path that tends tofollow a random walk makes these residual effects less obvious to thehuman eye.

FIGS. 28 a-28 b illustrate methods to stitch a segment of adjacentimaging areas according to embodiments of the present invention. Inparticular, FIG. 28 a illustrates a method for creating horizontalstitching paths, such as line segments BC, DE in FIG. 27 b, and JK inFIG. 27 d. In the example shown in FIG. 28 a, a stitching path (2804)traverses within the overlapping region 2802 between two adjacent SLMs.The overlapping region 2802 is bounded by a high cost function 2806 toprevent the stitching path from going out of the overlapping region. Thewidth of the overlapping region may be 1/10^(th) of the width betweentwo SLMs. In one embodiment, the width is approximately 8 mm. Inaddition, the stitching path is typically centered on the theoreticalboundary 2808 between the two imaging areas of the two adjacent SLMs. I

As shown in FIG. 28 a, the method generates a random stitching path 2804that emulates a horizontal line segment. The random stitching path maybe implemented as a set of diagonal lines that goes up and down from oneend to the other end. In some embodiments, each diagonal line may haveits corresponding angle (with respect to vertical axis, not shown), andthe angle may be different for each diagonal line. In other embodiments,for simplicity, an angle of 30 degrees (with respect to the verticalaxis, not shown) may be used. The direction of the diagonal lines isalternated (i.e. up and down) and the length of the diagonal lines aregenerated randomly using a random number generator with for example, anexponential distribution function as shown in FIG. 28 b.

FIG. 28 b illustrates that the length of the diagonal lines of thestitching path are exponentially distributed, where a mean length isused to define the exponential distribution. Using the exponentialdistribution function and a random number generator, diagonal lines ofvarious lengths as shown in FIG. 28 a may be generated. In one example,the value of the mean length may be a parameter defined by the user tobe 150 um. In yet another example, the angle of the diagonal lines mayalso be a parameter defined by the user to be 30 degrees. Note that,based on input from the high cost function 2806, the method may truncatethe exponential distribution to ensure the diagonal lines do not crossthe boundaries of the overlapping region.

Note that the goal of creating the stitching path is not to connect twopoints, unlike some routing algorithms, but to create an image withreduced amount of artifacts. There is no structure within theoverlapping region that blocks the stitching path going from one end tothe other end. Thus, the method of creating stitching path does notinvolve any backward or back track movement in order to avoid a blockagealong the way, unlike some routing algorithms. Furthermore, the purposeof the stitching path is not for connecting a pair of starting andending points. Thus, the starting point may be a random or may be apoint that generates the lowest cost path.

FIGS. 29 a-29 b illustrate other methods for stitching a segment ofadjacent imaging areas according to embodiments of the presentinvention. Similar to FIG. 28 a, FIG. 29 a illustrates a method thatgenerates a random stitching path 2902 that emulates a vertical linesegment centered on a theoretical boundary 2904 between two adjacentimaging areas. The random stitching path 2902 may be implemented as aset of diagonal lines confined by a set of boundary lines 2906. In someembodiments, the direction of the diagonal lines is alternated (i.e.left and right) and the length of the diagonal lines are generatedrandomly using a random number generator with an exponentialdistribution function as shown in FIG. 28 b.

FIG. 29 b illustrates a method for computing costs associated with eachdiagonal line segment according to embodiment of the present invention.As shown in FIG. 29 b, a portion of the stitching path 2902 ishighlighted in bold as the line segment 2908. This line segment 2908 isgenerated using a grid 2910. In one approach, on each grid point, themethod computes cost functions associated with that grid point and movesfrom one grid point to the next grid point, where the stitching path maygo. At each grid point, all possible choices for the next move areevaluated according to a set of cost functions. The lowest cost path isselected to be the next point on the path. A sample of cost computationfor the bottom diagonal line of the stitching path is shown as a seriesof steps 2912, where each movement in the horizontal direction isrepresented by delta x and each movement in the vertical direction isrepresented by delta y (2914). This process repeats such that a frontierof possible cost paths is determined, and the method expands thefrontier until it reaches the other end of the overlapping region. Then,the lowest cost path is chosen to be the stitching path.

In constructing the stitching path, a set of cost functions areevaluated and their outcome are used to determine the overall lowestcost path. In one embodiment, for certain length of motion along astitching path, costs are assigned using an expression of the form:

Cost=∫Cref×|(D+Dmin)/Dref|

pdx

where Cref is the cost per unit length at a reference distance; D is adistance measure as described below; Dmin is a minimum constant to avoidthe cost function from being infinite; Dref is a reference distance; pis a exponent factor, and dx is the incremental change in the xdirection (for a horizontal movement, as in the horizontal steps of thepath 2912). Note that for vertical movement steps, such as the verticalsteps of the path 2912, a vertical increment dy is evaluated instead. Inone approach, with D representing the distance to the random walk ofFIG. 28 a or FIG. 29 a, the parameters Cref=10 units per length,Dref=100 um, Dmin=0 um, and p=2 are used for calculating the costassociated with distance away from the random walk. The choice of apositive exponent p means that the cost increases when the stitchingpath moves away from the random walk, thus favoring stitching paths thatresemble the random walk.

In another approach, with D now representing the width of the figure orgap through which the candidate stitching path moves, the parametersCref=10 units per length, Dref=50 um, Dmin=10 um, and p=−2 are used forcalculating cost of a stitching path passing through a figure withnarrow width. In yet another approach, with D representing the distancebetween the candidate stitching path and the nearest figure edge, theparameters Cref=10 units per length, Dref=5 um, Dmin=1 um, and p=−2 areused for calculating cost associated with edge proximity. Taking thecosts of such situations into consideration, the method can avoidpassing through narrow figures or being in close proximity to edges.Note that Dref is typically chosen to ensure the stitching path is ableto pass through figures, and Dmin is typically chosen to be about1/10^(th) of Dref. Also, Dmin may be chosen to be on the order ofmagnitude of the grid size, such as 5 um. The choice of a negativeexponent p in these cost terms means that the cost increases as thefigure width decreases or the distance from the stitching path to afigure edge decreases, causing stitching paths that pass through themiddle parts of wide figures or gaps to be favored.

In yet another approach, a cost is associated with each unit ofincrement of the grid 2910, such as cost per unit distance may be setto 1. This cost term is proportional to the length of the stitchingpath, disfavoring back-and-forth movements. In yet another approach, acost of 0.5 is associated with each turn of the stitching path. Thiscost would have an effect to reduce the number of steps in the stitchingpath where it follows a diagonal segment of the random walk (see 2912).

FIGS. 30 a-30 d illustrate methods for imaging an object according toembodiments of the present invention. In an exemplary approach shown inFIG. 30 a, the method starts in block 3002 and then moves to block 3004where the method chooses evaluation points along edges of an object tobe imaged. FIG. 30 b illustrates an example of choosing evaluationpoints along edges of an object. As shown in FIG. 30 b, a trapezoidrepresents the object 3022 to be imaged. Evaluation points (black dots)3024 are selected and used for monitoring the exposure at the edges ofthe object 3022. Locations of the object 3022 are referenced to a pixelgrid 3026, where each square 3028 in the pixel grid 3026 represents apixel. A data structure may be created to store information associatedwith each evaluation point, including the location of each evaluationpoint relative to the pixel grid, the angle of an edge relative to thepixel grid, and the number of times an evaluation point is within anexposure field (i.e. the number of times an evaluation point has beenexposed), and the exposure dose accumulated at this evaluation point sofar. According to embodiments of the present invention, the distancebetween any two evaluation points 3024 is less than half a pixel and thedistance between evaluation points is equally spaced. In other words,the evaluation points are selected in such a way that the Nyquistcriterion is met, as the sampling frequency of the object 3022 to beimaged is higher than twice the frequency of the original signal asrepresented by the frequency of the pixel grid. In otherimplementations, the distance of evaluation points may be chosen to be⅓, ¼, or other fractions of a pixel as long as the Nyquist criterion ismet.

In block 3006, the method performs an exposure to image the object 3022.Within each exposure performed by the block 3006, the method furtherperforms the following operations. First, in block 3012, the methodfirst fills the interior pixels of the object 3022 using a scan linegeometric algorithm for example. This is shown by the shaded area 3030in FIG. 30 b. Note that the example shown in FIG. 30 b assumes an imagetransition from white to black, where multiple dosages of exposures maybe received within the boundaries of the object 3022. Persons skilled inthe art would appreciate that a similar but inverse operation may beperformed to image an object that has a transition from black to white.

In block 3014, the method examines the edge pixels of the object andmakes exposure adjustments according to a number of factors, includingthe area of a partial edge pixel with respect to the pixel grid, thecurrent exposure dosage level with respect to a target exposure dosagelevel, the influence of exposures from neighboring pixels, the amount oferror/distortion corrections, and other performance optimizationconsiderations. If a pixel is primarily outside the edge (and itscorresponding evaluation points) of the object, for example pixel 3025in FIG. 30 b, dithering of the associated evaluation points is turnedoff for most of the exposures. On the other hand, if a pixel isprimarily inside the edge (and its corresponding evaluation points) ofthe object, for example pixel 3027 in FIG. 30 b, dithering of theassociated evaluation points is turned on for most of the exposures.

In block 3016, the method accumulates exposure dosage of the imagingwriter system. FIG. 30 c and FIG. 30 d illustrates such accumulation ofexposure dosage from an initial dosage level to a target exposure dosagelevel. In both scenario shown in FIG. 30 c and FIG. 30 d, although thetotal amount of exposure dosage is the same (target exposure dosage),different effects of edge transitions may be achieved by adjusting theedge pixels for each exposure. The accumulation and use of the exposuredosages from each exposure provides a feedback mechanism to allow theimaging writer system to adaptively adjust imaging profile at theboundaries of the object being imaged and at the same time ensure thetotal target exposure dosage is maintained. In block 3018, the methodmoves the pixel grid 3026 for subsequent exposure. This is furtherdescribed in association with FIGS. 33 a-33 d below.

In block 3008, a determination is made as to whether a predeterminedtarget exposure count has been reached. If the target exposure count hasnot been reached (3008_No), the method moves to block 3006 and performsanother exposure to image the object 3022. In such a way, multipleexposures are performed in order to image an object. Alternatively, ifthe target exposure count has been reached (3008_Yes), the method movesto block 3010 and imaging operation of the object is ended.

According to embodiments of the present invention, multiple exposuresmay be performed on the object. Such multiple exposures may be achievedby multiple passes of an imaging area by different SLMs to provide apredetermined amount of exposure to the imaging area of interest. In oneimplementation, about 400 exposures may be performed for each imaginglocation, and the dosage of each exposure is accumulated at eachevaluation point. Typically, the first exposure is arbitrary. Forsubsequent exposures, the method compares the accumulated dosage at animaging location to a fraction of the target exposure dosage(N/400*total target exposure dosage) for that imaging location. If theaccumulated dosage is lower than the target exposure dosage, then thepixel may be turned on for that exposure. On the other hand, if theaccumulated dosage is higher than the target exposure dosage, then thepixel may be turned off for that exposure. For subsequent exposures, themethod compares the accumulated dosage at an imaging location to afraction of the target exposure dosage for that imaging location,pro-rated by the number of exposures completed (for exposure N of 400,compare against N/400*total target exposure dosage).

According to embodiments of the present invention, FIG. 30 c and FIG. 30d illustrate different implementations in adjusting the edge pixels. InFIG. 30 c, the vertical axis represents the accumulated amount ofexposure dosage, and the horizontal axis represents the number ofexposures administered during the imaging process of the object 3022. Inthis example, the exposure dosage increases relatively linearly as thenumber of exposures increases. The exposure dosage of an edge increasesfrom an initial dosage level to the target exposure dosage following thestep function 3032. As a result, a smeared or smoothed transition isproduced at the edges of the object being imaged. Note that the totaltarget exposure dosage may be determined experimentally, theoretically,or determined by a combination of experimental and theoreticallyanalysis prior to performing the multiple exposures. In otherapproaches, the exposure dosages in early exposures may overshoot orundershoot relative to the step function 3032. However, such exposuredosage overshoot or undershoot may be corrected in subsequent exposuresas the number of exposure count increases, and converge to the targetexposure dosage towards the end of the exposure count.

On the other hand, in FIG. 30 d, the amount of exposure dosage increasesslowly initially, then increases relatively sharply in the mid sectionof the exposures, and slows down towards the end of the exposures, asshown by a step function 3034. This or any other step function can beused, provided it ends at the desired target dosage. An exemplary totaltarget dosage may be 20 milli-Joules per square centimeter (mJ/cm²).

In the examples of FIG. 30 c and FIG. 30 d, the threshold ratio for eachexposure may be controlled. For example at the boundary of an object, ifa pixel is primarily outside the edge (and its corresponding evaluationpoints) of the object, for example pixel 3025 in FIG. 30 b, thethreshold ratio of exposure may be set higher to create a higherprobability that the pixel would be turned off. But if a pixel isprimarily inside the edge (and its corresponding evaluation points) ofthe object, for example pixel 3027 in FIG. 30 b, the threshold ratio ofexposure may be set lower to create a higher probability that the pixelwould be turned on. In situations where an edge (and its correspondingevaluation points) falls roughly in the middle of a pixel, for examplepixel 3029 in FIG. 30 b, then the pixel will be turned on forapproximately half of the exposures and the pixel will be turned off forapproximately the other half of the exposures. By adjusting thethreshold to favor exposing an edge pixel when the pixel grid is suchthat the majority of the pixel is in the interior, instead of simplyexposing the edge pixel in any intermediate exposure where the dosage isfound to be below target, a sharper image profile at the edge can beobtained.

FIGS. 31 a-31 b illustrate methods for computing the accumulated dosageat evaluation points according to embodiments of the present invention.The method computes the accumulated dosage for evaluation points withina pixel P 3102 by taking into consideration contributions by exposuresof that pixel and its neighboring pixels. In one implementation, dosagecontributions to locations within pixel P3102 from its immediateneighboring pixels N1 3104 and second neighboring pixels N2 3106 aredetermined and stored. In general, the contribution of a pixel to itsneighbors may have a waveform of shape similar to (SinX/X)², and thecontribution diminishes significantly outside of the second orderneighbors N2 3106. In the example shown in FIG. 31 a, the width of apixel is chosen to be 1 square micron and the contributions of pixel P3102 to its neighbors 2 um away is negligible. In other embodiments,effects of the pixel P 3102 to higher orders (3^(rd) order or higher)may be considered based on desired accuracy of the image writer system.

As shown in the example of FIG. 31 a, a pixel may be further quantizedto a granularity of ⅛ of a pixel, shown by the sub-pixel grid 3108, totake into account of finer accuracy in imaging the pixel P 3102. Thedosage contribution of each neighboring pixel is pre-computed at each ofthese finer grid points, and the value at the nearest of these points(or a combination of a few nearest finer grid points) is used whenaccumulating the dose at an evaluation point. Depending on the accuracyrequirement of the image writer system, the pixel P may be quantized to1/16 (shown by the numeral 3110) or other finer quantization factorsaccording to embodiments of the present invention.

Prior to imaging an object, simulations are performed to collectinformation to create a series of lookup-tables (LUTs). The LUTs areused to compute the exposure dosage for each exposure of the objectduring imaging operations. In one approach, a LUT may be created asfollows. As discussed in association with FIG. 31 a above, an exposureof a pixel may have contributions to its first order neighbors (N1) andsecond order neighbors (N2). Each pixel may be further divided into 64sub-pixel regions, using a quantization granularity of ⅛ of a pixel. Inaddition, 400 exposures may be accumulated for one imaging area and athreshold ratio is about half of its total exposure intensity. Thus,each exposure may deliver 1/800^(th) of the complete exposure. Assuminga 2.5% ( 1/40) precision for each exposure, then the method needs toquantize to 1/32,000 of a full dose, which may be represented byapproximately 15 bits. Rounding the 15 bits to 16 bits, it means that 16bits (2 bytes) may be used to represent the dose contribution of onepixel at each of the 64 sub-pixel location. In other words, for eachevaluation point considered in the imaging process, a 5×5 array ofpixels are being examined; each pixel has 64 sub-pixel regions; and eachsub-pixel region is represented by 2 bytes. As a result, each table mayhave a size of approximately 3200 bytes (25×64×2). Person skilled in theart would appreciate that to achieve different desired accuracy, adifferent array (e.g. 6×6, 8×8, etc) of pixels may be considered;different number of exposures (e.g. 500, 1,000, etc.) maybe taken;different precision percentage (e.g. 1%, 2%, etc) may be used, anddifferent number of bits (e.g. 20, 21 bits, etc) may be used torepresent each of the 64 sub-pixel location. For example, for theexample of 21 bits representing a sub-pixel region, a 64-bit long wordmay be used to represent three of such sub-pixel regions. Depending onthe desired accuracy of the image writer system, corresponding LUTshaving different sizes may be created.

For the example shown in FIG. 31 a, to calculate the dose contributed byan exposure at each evaluation point would require 25 table lookupsusing conventional approaches, which include table lookups forneighboring pixels (N1 s, and N2 s) of the pixel P 3102. Such approachesmay take a long time and consumes lots of processing power. FIG. 31 billustrates a method for processing the pixel P of FIG. 31 a accordingto an embodiment of the present invention. In one approach, the pixel P3102 and its first order neighbors N1 and second order neighbors N2 maybe arranged in five rows of five pixels, which are shown in FIG. 31 b as3112, 3113, 3114, 3115, and 3116 in FIG. 31 b. The lookup table 3118 maybe arranged in such a way that each table lookup would retrieveinformation for a row of five pixels. Note that in this approach,instead of having 25 separate tables for each pixel, a combined table ofroughly 100K bytes (3.2K×32) may be created and used for retrievinginformation for a 5-pixel group together. In such a way, the efficiencyof performing table lookup may be increased by a factor of 5.

In yet another approach, the lookup table 3118 may be arranged in adifferent way that each table lookup would retrieve information for acolumn of five pixels. In that approach, the pixel P 3102 and its firstorder neighbors N1 and second order neighbors N2 may be arranged in fivecolumns of five pixels (not shown). To access the lookup table 3118,part of the address may be derived from bit pattern of a column of fivepixels. For example, a bit pattern of 10101 may be used to represent acolumn of five pixels, where a bit value of 1 may indicate a pixel is ONand a bit value of 0 may indicate a pixel is OFF, or vice versa based ondesign engineers' implementation choices. With the arrangement of groupof five pixels, each table lookup is more efficient because it iscapable of retrieving data for five pixels instead of retrieving datafor one pixel in conventional approaches.

Note that the distance between evaluation points is substantially thesame and they are chosen to be close to each other. Taking theseproperties into consideration, FIG. 32 illustrates methods for imagingobjects by processing a group of evaluation points according toembodiments of the present invention. In this example, two objects 3202and 3204 are being imaged and they are referenced by a pixel grid 3206.As described above, evaluation points, represented by black dots, arechosen along the boundaries of each object. In one implementation, theevaluation points may be processed in groups of four and correspondinglookup tables may be constructed for processing particular types ofedges. For example, a lookup table 3208 may be provided for processinghorizontal edges; a lookup table 3210 may be provided for processingvertical edges; a lookup table 3212 may be provided for processing edgeswith angle A 3212, and a lookup table 3214 may be provided forprocessing edges with angle B 3214, etc. As seen in this example, thenumber of tables may depend on a number of factors, such as the shapes(angles of edges) of objects to be imaged. In general, a reference tableis created for the whole image writer system and various compositetables, such as tables 3208, 3210, 3212, and 3214, are created foraddressing different situations.

As shown in FIG. 32, a group of 4 evaluation points may be processed asa group. Taking the group of 4 evaluation points oriented vertically forexample, which may span a distance of approximately less than 2 pixels.Note that in some situations, a group of 4 evaluation points may spanover 3 pixels; and in those situations, the 3 pixels and theircorresponding neighboring pixels will be considering in imaging thegroup of 4 evaluation points. Assuming a pixel may be affected by itsneighbors from 2 pixels away, 2 neighboring pixels are appended on eachend of the 4 vertical evaluations points to form a group of 6 to 7vertical pixels. According to embodiments of the present invention, thelookup table for vertical edge may be created to allow storing andretrieving the dose contributions to 4 vertical evaluation points at atime. Since each of these dose contributions may be represented by 16bits, the group of 4 vertical evaluation points may be combined to forma long word of 64 bits, as shown by the numeral 3217. In such a way, tocompute the group of 4 vertical evaluation points for imaging, about 6to 7 table lookups are performed as opposed to the conventional methodof each evaluation point would require 5 table lookups, which is animprovement of by a factor about 3 times. With the above description,person skilled in the art would appreciate that the similar approach maybe applied to create a table for certain specific angle, such as alookup table for horizontal edge 3208, a lookup table for angled edge A3212, and a lookup table for angled edge B 3214, etc.

Note that each long word of 64 bit is constructed in such a way thateach of the 16 bit unit would not overflow during simulation. This isdone by controlling the scaling of each dose value represented by the 16bit word. By packing the dose contributions for 4 evaluation points in along word of 64 bits, the size of the table is increased by a factor of4. Taking the table described in association with FIG. 31 for example,the new table size would be 400K bytes (100K×4). Also note that an edgeof an object may not always be broken up to groups of 4 evaluationpoints. To address the remainder evaluation points near the end of anedge, such remainders may still be processed as a group of 4 evaluationpoints, except nothing would be done with the evaluation points that arenot being used (“don't care” evaluation points). For example, the tophalf of the 64 bit long word is not used and masked out. In the specialcase that an edge goes off at a weird angle for which no special tablewas constructed, that edge's evaluation points can be divided intogroups of 1, and simulated using the tables for any edge angle, withonly 1 evaluation point used in each group of 4 evaluation points. Thusthis edge may still be processed using the method described above, butonly one evaluation point will be processed at a time and 3 of the 4evaluation points are ignored. In this special case, a very smallpercentage (perhaps 1%) of the cases would be three times slower, butthen special tables only need to be constructed for the common edgeangles found in the design. Note that it is important to control thesize of the lookup tables such that they can be stored in cache memoryto avoid retrieving data from disk during simulation. For example, whenprocessing horizontal edges, the lookup table for horizontal edge 3208should be cached; when processing vertical edges, the lookup table forvertical edge 3210 should be cached.

It is desirable to minimize the amount of data created during imageprocessing. This is important because it would reduce the time spent inadjusting edge pixels 3014 and accumulating exposure dosage 3016 asdescribed in association with FIG. 30 a. In addition, it would reducethe amount of data transmission to each of the SLMs. FIGS. 33 a-33 dillustrate methods for optimizing imaging objects according toembodiments of the present invention. In the example shown in FIG. 33 a,objects 3301 and 3303 to be imaged are referenced by a pixel grid 3302(grid not shown for better illustration, but it is similar to the oneshown in FIG. 30 b). In other embodiments, one or more objects may bereferenced by the pixel grid 3302 and be processed simultaneously. It isassumed that multiple objects may occupy any area within the pixel grid3302. In one implementation, the pixel grid 3302 has a width of 768pixels and length of 1024 pixels. In other implementations, pixel gridsof different sizes may be employed. For the first exposure, every pixelposition of the entire pixel grid is computed and the results ofcomputation are stored.

After the first exposure, the pixel grid 3302 is shifted horizontally byan amount of Delta X 3305 and vertically by an amount Delta Y 3307. Inone, implementation, the amount of Delta X 3305 may be 8.03 pixels andthe amount of Delta Y 3307 may be 0.02 pixels. Note that the offsetsDelta X and Delta Y are not integer multiple of pixels. The intent is toachieve consistency in imaging all figure edges. If the offsets werechosen to be integer multiple of pixels, the pixel grids would bealigned from one to the other. In that case, if an edge falls on thepixel grid, a sharper edge may be imaged; but if an edge fallsin-between the pixel grid, a blurrier edge may be imaged. With offsetsbeing non-integer multiple of pixels, the edges are imaged in similarmanner when about 400 exposures are overlaid and accumulated, withdifferent pixel grid positions, having the edges fall on pixelboundaries occasionally and fall in other locations of a pixel at othertimes. This method of jittered pixel averaging (JPA) provides sub-pixeledge position resolution, with consistent imaging performance for alledges.

FIG. 33 b illustrates the pixel grid 3302 has shifted by Delta X andDelta Y and is shown as 3304. Note that this drawing is not to scale andthe amount of Delta X and Delta Y have been exaggerated for illustrationpurposes. In general, the pixel grid may be shifted by a small amountfrom one pixel location (as in FIG. 33 a) to a next pixel location (asshown in FIG. 33 b) so that majority of computations performed for theprevious exposure may be used for the current exposure. Therefore, theamount of computation is minimized. Note that the vertical shift ismerely 0.02 pixels, which is practically negligible, even after a fewvertical shifts. Within the pixel grid 3304, pixels in the leftmoststrip 3306 (8.03×1024) are computed because it may be the last time theexposure dosage for these pixels are computed and adjusted (pixels to beshifted-out of the pixel grid). The rightmost strip 3310 (8.03×1024) arealso computed because these pixels are newly introduced and have notbeen computed previously (pixels shifted-in). The middle strip 3308(approximately 752×1024, shaded, also known as overlapping pixels) arecopied from the previous computation performed in FIG. 33 a. Since themiddle strip 3308 is not recomputed each time the pixel grid is shifted,performance of the image writer system is significantly improved.

FIG. 33 c illustrates the pixel grid 3304 has shifted by another Delta Xand Delta Y and is shown as 3312. Similarly to the situation in FIG. 33b, within the pixel grid 3312, pixels in the leftmost strip 3314(8.03×1024) are computed because it may be the last time the exposuredosage for these pixels are computed and adjusted. The rightmost strip3318 (8.03×1024) are also computed because these pixels are newlyintroduced and have not been computed previously. The middle strip 3316(approximately 752×1024, shaded) are copied from the previouscomputation performed in FIG. 33 b.

FIG. 33 d illustrates the pixel grid 3312 has shifted by another Delta Xand Delta Y and is shown as 3320. Similarly to the situation in FIG. 33c, within the pixel grid 3320, pixels in the leftmost strip 3322(8.03×1024) are computed because it may be the last time the exposuredosage for these pixels are computed and adjusted. The rightmost strip3326 (8.03×1024) are also computed because these pixels are newlyintroduced and have not been computed previously. The middle strip 3324(approximately 752×1024, shaded) are copied from the previouscomputation performed in FIG. 33 c. After three successive shifts of thepixel grid, the process may start anew and repeat the processesdescribed in FIGS. 33 a-33 d.

One of the benefits of copying pixels from a previous exposure is thatthe processes of filling interior pixels 3012 and adjusting edge pixels3014 as described in association with FIG. 30 a may be skipped. Inaddition, the computation associated with block 3016 may be optimized bycreating another dose table that represent the effect of four exposures,with constant pixel data and with the known Delta X and Delta Y valuesbetween them. Then for the pixels that are kept unchanged within a groupof four exposures, a single set of table lookups may be performed inblock 3016 instead of performing four sets of table lookups. Anotherbenefit is that the amount of data transmission to SLMs is reduced. As aresult, the overall performance of the image writer system is increased.A tradeoff resulted from copying pixels from a previous exposure is thatboth exposures assumes the same amount of dosage, which means there isfewer opportunities to adjust brightness of the edges. However, in asystem having about 400 exposures, this is a small compromise in edgeresolution for a large gain in system performance.

Note that after three successive shifts, the total amount of shifts inthe Y direction is 0.06 pixels, which is a negligible amount. The totalamount of shifts in the X direction is 24.09 pixels, and these pixelsare being tracked closely and computed after each shift of the pixelgrid. FIGS. 33 a-33 d illustrate a system implementing a sequence ofthree shifts. Applying the same principle, person skilled in the artwould appreciate that a system may be designed to implement differentnumber of shifts, such as one, two, four, or other number of shifts. Inaddition, different Delta X and Delta Y values, such as 8.10 pixels forDelta X and 0.03 pixel for Delta Y may be used.

When the image writer system is built, various sources of inaccuraciesmay be introduced, such as inaccuracies in the alignment of the variouscomponents used in the system, inaccuracies from manufacturing defectsof the lenses and other optical components. The following sectionsdiscuss methods to determine and correct such inaccuracies according toembodiments of the present invention.

To determine the accuracy of the image writer system, measurements aremade to determine: 1) distances between adjacent SLMs; 2) amount ofrotation or tilt of the DMD mirror array; and 3) amount of opticalmagnification/reduction from a SLM (DMD) to the substrate. In oneapproach, known patterns are placed on the stage and measurements aremade to collect data of the above parameters of interest. Images aretaken through the lens of a SLM, and the size of a camera pixel in realterms may be determined. To measure rotation/tilt of a SLM, a Fouriertransformation is performed on the collected data to determine the angleof rotation. In another approach, a premade calibration substrate may beplaced on stage and examined at first through lens camera from thecenter point of view. Then move the stage by certain predetermineddistances along a user defined axes (for example by delta x, and deltay), and repeat the examination of the premade calibration substratethrough the camera of each SLM.

After the parameters of the system have been measured, such data can beused to correct inaccuracies of the system. In one approach, thesubstrate may be divided into areas to be imaged by corresponding SLMs.Based on the spacing of 100 mm between the SLMs, the system providessufficient overlap between two adjacent SLMs, for example up to a fewmillimeters, to ensure any area of the substrate can be adequatelycovered by displacing a pattern correspondingly in the coordinate spaceof the SLMs. In another approach, when a pixel grid is placed on thesubstrate, the pixel grid may be expanded or contracted to correct themagnification/reduction variation from a SLM to the substrate. Forexample, if a target reduction ratio is 10:1, a reduction ratio of10.1:1 would have introduced a 1% variation to the optical path and suchvariation may be compensated by the pixel grid. In yet another approach,the location of a reference evaluation point is determined, and then thedistance and/or angle of a corresponding evaluation point can bedetermined using the reference evaluation point and the variations dueto the inaccuracies measured from the actual system. Note that suchcorrections would typically affect the edges of objects, the basic flowof the imaging process as described in association with FIG. 30 a wouldremain the same.

In addition to the inaccuracies from the assembly of the system,distortions may be introduced by the lenses or other elements in theprojection mechanism. According to embodiments of the present invention,a distortion effect, such as pin cushion distortion, may be described asa location in polar coordinate, where r is modified by certain amount,for example, r′=r−0.02*r³). Note that this approach of correctingdistortion error is similar to the approach of correcting a scalingerror. In both cases, in order to determine which pixel an edge (orevaluation point) is in, the method needs to measure the size of thepixel, which may have changed slightly due to geometric variations andother effects.

In practice, the amount of distortion is related to the quality oflenses used in the imaging writer system, with high-quality lensesproducing less distortion. Such distortion may be determined bysimulation during the design process, or by measurement after the lensesare made. In one approach, an image writer system may use reasonablyhigh quality lenses and apply the methods described herein to correctthe relatively small fraction of distortions. To correct errors due todistortion, the system first determines the function of the distortion;it then applies an inverse function of the distortion when imaging theobject to correct the distortion. Note that, this approach of correctingdistortions may be applied to other forms and shapes of distortions, aslong as the distortion function is found, an inverse function may becreated to correct the distortion. This approach is further described inassociation with FIG. 34 below.

FIG. 34 illustrates methods for making corrections to the opticalimaging writer system according to embodiments of the present invention.In the example shown in FIG. 34, the numeral 3402 represents asimplified pixel grid and the numeral 3404 represents a distorted pixelgrid. The numeral 3406 represents an object to be imaged and the numeral3408 represents an inverse function for correcting distortion of theobject 3406. Note that, near the middle, the center square of thedistorted pixel grid 3404 is substantially the same as the originalpixel grid 3402. But out at the corner, the “square” of the distortedpixel grid looks more like trapezoidal. Person skilled in the art wouldappreciate that other form and shape of pixel grid may be used, such asa rectangular pixel grid having a size of 1024×768 pixels.

Note that the pixel grid 3402 describes an area to be imaged with oneSLM or describes a portion of an area to be imaged by the SLM. Indifferent exposures administered by the SLM, the area described by thepixel grid may be moved around relative to the location of the SLM andits exposure field. Thus, the shape of the distortion may changedepending on the location of the SLM and exposure. In general, an areanear the middle gets little distortion; but an area near the cornersgets more distortion.

As shown in the example of FIG. 34, in order to sample the object 3406,the system transforms the coordinates of the object into coordinates ofthe SLM array, which is represented by the transformation of the objectfrom 3406 to 3408. In essence, the system takes the shape of the object3406, distorting it in an inverse way (represented by 3408), and thenthe distorted lens of the SLM, which sees the original pixel grid 3402in the form of distorted pin cushion 3404, may be used to image theobject.

As described in FIGS. 30 a and 30 b, evaluation points are chosen alongthe edges of the object 3406. The circular region 3409 illustrates asmall section of the edges 3406 and its corresponding inverse function3408. The numeral 3410 represents four evaluation points along theobject 3406 and the numeral 3412 represents corresponding fourevaluation points would fall along the inverse function 3408. Thecircular region 3409 is enlarged and shown on the right hand side ofFIG. 34.

Note that for the groups of 4 evaluation points, the spacing betweenthem is determined by Nyquist theory of maximum resolution of the lens.Typically, the spacing between evaluation points may be a fraction of apixel, such as ½ or ⅓ of a pixel, etc. In such situations, thedistortion may be even smaller fraction of a pixel. Over the range ofthe distance of four evaluation points, the distortion is likely to bevery small, for example in the order of 1/25 of a pixel, and thecurvature of the four evaluation points due to distortion may benegligible.

As shown in the circle of FIG. 34 (drawing not to scale, with thedistortion exaggerated), the four exemplary evaluation points along avertical line 3414 on the left hand side may be mapped to fourevaluation points along a distorted line 3416 on the right hand side toform an inverse of the distortion function. Accordingly, the centerpoint 3418 of the vertical line is mapped to the center point 3420 ofthe distorted line, which acts as a reference of the 4 evaluation pointsof the distorted line. Note that FIG. 34 has exaggerated the deviationof the evaluation points from the distorted line. According toimplementations of the present invention, the deviation is very small,typically less than about 0.1 percent of a pixel off from the referencecenter point 3420. With the above framework, the group of four distortedevaluation points may be computed using the methodologies describedabove from FIG. 30 to FIG. 33.

According to embodiments of the present invention, considering the groupof four evaluation points in view of the quantization of ⅛ pixel asdiscussed in association with FIG. 31 a, if there is a distortion of1/25 of a pixel, and the center point is snapped to the ⅛ of a pixelgrid, which gives an error of 1/16 of a pixel. Over the course ofimaging through multiple exposures with different SLM and exposurelocations, there is a tendency for these errors to cancel out eachother. For example in some exposures, the SLMs may be tilted one way,and in other exposures the SLMs may be tilted the other way. As aresult, the image may get a smoothed edge. In other words, the errorsmay be averaged out, which is in addition to the situation that they maybe small enough to be considered negligible. In the process ofdetermining which ⅛ of pixel grid the 4 evaluation points falls on, thecorrection is made using the new location of the center of the distorted4 evaluation points 3420. Note that in this example, the center point1420 may be shifted both vertically and horizontally.

Embodiments of the present invention not only are applicable andbeneficial to the lithography for manufacturing of FPD and mask for FPDmanufacturing, the making of one-of-the-kind or precision duplicates oflife-sized art on glass substrate, they are also applicable andbeneficial to the manufacturing of integrated circuits, computergenerated holograms (CGH), printed circuit board (PCB), for largeimaging display applications in both micro and meso scales.

Embodiments of the present invention are further applicable andbeneficial to lithography manufacturing processes without using mask,such as writing intended mask data patterns to substrates directly. Inthis way, the mask cost and associated issues of concern are eliminated.Embodiments of the present invention enable exposure tools for mask-lessexposure that exceeds the throughput requirements for the upcoming G10and beyond. More importantly, this configuration comes with improvedprocess window to ensure better lithography yield.

It will be appreciated that the above description for clarity hasdescribed embodiments of the invention with reference to differentfunctional units and processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits or processors may be used without detracting from the invention.For example, functionality illustrated to be performed by separateprocessors or controllers may be performed by the same processors orcontrollers. Hence, references to specific functional units are to beseen as references to suitable means for providing the describedfunctionality rather than indicative of a strict logical or physicalstructure or organization.

The invention can be implemented in any suitable form, includinghardware, software, firmware, or any combination of these. The inventionmay optionally be implemented partly as computer software running on oneor more data processors and/or digital signal processors. The elementsand components of an embodiment of the invention may be physically,functionally, and logically implemented in any suitable way. Indeed, thefunctionality may be implemented in a single unit, in a plurality ofunits, or as part of other functional units. As such, the invention maybe implemented in a single unit or may be physically and functionallydistributed between different units and processors.

One skilled in the relevant art will recognize that many possiblemodifications and combinations of the disclosed embodiments may be used,while still employing the same basic underlying mechanisms andmethodologies. The foregoing description, for purposes of explanation,has been written with references to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described to explain the principles of theinvention and their practical applications, and to enable others skilledin the art to best utilize the invention and various embodiments withvarious modifications as suited to the particular use contemplated.

1. A method for processing image data in a lithography manufacturingprocess, comprising: providing a parallel imaging writer system, whereinthe parallel imaging writer system includes a plurality of spatial lightmodulator (SLM) imaging units arranged in one or more parallel arrays,and wherein each of the plurality of SLM imaging units includes one ormore illumination sources, one or more alignment sources, one or moreprojection lenses, and a plurality of micro mirrors configured toproject light from the one or more illumination sources to thecorresponding one or more projection lens, wherein each SLM imaging unitis individually controlled; receiving a mask data pattern to be writtento a substrate; processing the mask data pattern to form a plurality ofpartitioned mask data patterns corresponding to different areas of thesubstrate; identifying one or more objects in an area of the substrateto be imaged by corresponding SLMs; selecting evaluation points alongedges of the one or more objects; configuring the parallel imagingwriter system to image the one or more objects using the evaluationspoints; and performing multiple exposures to image the one or moreobjects in the area of the substrate by controlling the plurality ofSLMs to write the plurality of partitioned mask data patterns inparallel.
 2. The method of claim 1, wherein selecting evaluation pointscomprises: selecting evaluation points having an equal distance from oneanother, wherein the equal distance between adjacent evaluation pointsis less than half of distance between adjacent pixels.
 3. The method ofclaim 2 further comprising: storing location of each evaluation pointrelative to a pixel grid; storing angle of an edge relative to the pixelgrid; and storing number of times an evaluation point has been exposed.4. The method of claim 1, wherein configuring the parallel imagingwriter system comprises: forming a set of lookup tables for processingpixels within the one or more objects, wherein the pixels are quantizedto form a plurality of sub-pixel regions, and each lookup table storesinformation for imaging the pixels and their corresponding sub-pixelregions.
 5. The method of claim 4, wherein the set of lookup tablescomprises: contributions to locations within a pixel from exposures ofneighboring pixels, including contributions from a first orderneighboring pixels having a distance of one pixel away from the targetpixel.
 6. The method of claim 5 wherein the set of lookup tables furthercomprises contributions from a second order neighboring pixels having adistance of two pixels away from the target pixel, and contributionsfrom higher order neighboring pixels having a distance of more than twopixels away from the target pixel.
 7. The method of claim 4, whereinconfiguring further comprises: forming the set of lookup tables forprocessing edges of the one or more objects having different angles. 8.The method of claim 4, wherein configuring further comprises: formingthe set of lookup tables for accessing information of multiple relatedpixels as a group.
 9. The method of claim 4, wherein configuring furthercomprises: creating an address for accessing information of multiplerelated pixels as a group from the set of lookup tables.
 10. The methodof claim 1, wherein configuring further comprises: identifying inherentinaccuracies of the parallel image writer system; creating adjustmentsto compensate for the inherent inaccuracies; and performing multipleexposures to image the one or more objects in the area of the substrateusing the adjustments.
 11. The method of claim 10, wherein identifyinginherent inaccuracies comprises: measuring distances between adjacentSLMs; measuring amount of rotations of DMD mirror array; and measuringoptical magnification factor from an SLM unit to the substrate.
 12. Themethod of claim 10, wherein creating adjustments to compensate for theinherent inaccuracies comprises: identifying functions describingboundaries of distorted objects; creating inverse functions forcompensating the boundaries of distorted objects; and applying theinverse functions in imaging the boundaries of distorted objects.
 13. Asystem for processing image data in a lithography manufacturing process,comprising: a parallel imaging writer system, wherein the parallelimaging writer system includes a plurality of spatial light modulator(SLM) imaging units arranged in one or more parallel arrays, and whereineach of the plurality of SLM imaging units includes one or moreillumination sources, one or more alignment sources, one or moreprojection lenses, and a plurality of micro mirrors configured toproject light from the one or more illumination sources to thecorresponding one or more projection lens, wherein each SLM imaging unitis individually controlled; a controller configured to control theplurality of SLM imaging units, wherein the controller includes logicfor receiving a mask data pattern to be written to a substrate; logicfor processing the mask data pattern to form a plurality of partitionedmask data patterns corresponding to different areas of the substrate;logic for identifying one or more objects in an area of the substrate tobe imaged by corresponding SLMs; logic for selecting evaluation pointsalong edges of the one or more objects; logic for configuring theparallel imaging writer system to image the one or more objects usingthe evaluations points; and logic for performing multiple exposures toimage the one or more objects in the area of the substrate bycontrolling the plurality of SLMs to write the plurality of partitionedmask data patterns in parallel.
 14. The system of claim 13, whereinlogic for selecting evaluation points comprises: logic for selectingevaluation points having an equal distance from one another, wherein theequal distance between adjacent evaluation points is less than half ofdistance between adjacent pixels.
 15. The system of claim 14 furthercomprising: logic for storing location of each evaluation point relativeto a pixel grid; logic for storing angle of an edge relative to thepixel grid; and logic for storing number of times an evaluation pointhas been exposed.
 16. The system of claim 13, wherein logic forconfiguring the parallel imaging writer system comprises: logic forforming a set of lookup tables for processing pixels within the one ormore objects, wherein the pixels are quantized to form a plurality ofsub-pixel regions, and each lookup table stores information for imagingthe pixels and their corresponding sub-pixel regions.
 17. The system ofclaim 16, wherein the set of lookup tables comprises: contributions tolocations within a pixel from exposures of neighboring pixels, includingcontributions from a first order neighboring pixels having a distance ofone pixel away from the target pixel.
 18. The system of claim 17 whereinthe set of lookup tables further comprises contributions from a secondorder neighboring pixels having a distance of two pixels away from thetarget pixel, and contributions from higher order neighboring pixelshaving a distance of more than two pixels away from the target pixel.19. The system of claim 16, wherein logic for configuring furthercomprises: logic for forming the set of lookup tables for processingedges of the one or more objects having different angles.
 20. The systemof claim 16, wherein logic for configuring further comprises: logic forforming the set of lookup tables for accessing information of multiplerelated pixels as a group.
 21. The system of claim 16, wherein logic forconfiguring further comprises: logic for creating an address foraccessing information of multiple related pixels as a group from the setof lookup tables.
 22. The system of claim 13, wherein logic forconfiguring further comprises: logic for identifying inherentinaccuracies of the parallel image writer system; logic for creatingadjustments to compensate for the inherent inaccuracies; and logic forperforming multiple exposures to image the one or more objects in thearea of the substrate using the adjustments.
 23. The system of claim 22,wherein logic for identifying inherent inaccuracies comprises: logic formeasuring distances between adjacent SLMs; logic for measuring amount ofrotations of DMD mirror array; and logic for measuring opticalmagnification factor from a SLM unit to the substrate.
 24. The system ofclaim 22, wherein logic for creating adjustments to compensate for theinherent inaccuracies comprises: logic for identifying functionsdescribing boundaries of distorted objects; logic for creating inversefunctions for compensating the boundaries of distorted objects; andlogic for applying the inverse functions in imaging the boundaries ofdistorted objects.